The present invention concerns an electronic timepiece, comprising a motor module driving hands. The term motor module is used to denote the assembly of the components of the watch, which, in the kinematic train, go from the motor to the spindles of the hands. The term "spindle" is used for convenience to embrace both arbor and pipe spindles. A motor module thus essentially comprises the motor with its rotor, the spindles for the hands, the train of gears (wheels and pinions) connecting the rotor of the motor to the spindles of the hands and the means for assembling those components and positioning them relative to each other.
In conventional watches, these various components are mounted in bridge members and plates which are rigidly fixed together. The resulting assembly forms the essential portion of the mechanical part of the watch movement.
In order to reduce the thickness of the watch and simplify the structure of the watch movement, it has already been proposed that the bridge members should be omitted. The wheels and the motor are directly mounted on the bottom of the watch casing and possibly on the internal surface of the dial of the watch. There is then no longer any movement in the true sense. This is disclosed in French patent application No. 79 21863. This construction permits a very substantial reduction in the overall thickness of the watch, but it makes the construction of the watch much more delicate.
For the same purpose, it has also been proposed that the wheels should be mounted on a single plate, in an overhung manner. The wheels are mounted pivotally on micro ball-bearing assemblies which are themselves mounted on lugs or studs forming an integral part of the plate. The wheel and pinions of the same gear are therefore necessarily disposed on the same side of the plate. Such a design is disclosed in Swiss patent No. 610 178. This design is once again fairly complex, both in regard to production and assembly of the watch. In addition, the Swiss patent only concerns a mechanical watch, and therefore does not solve the problem of fitting the motor.
French patent No. 76 15 399 describes a watch movement of conventional type, with two base plates, but in which the stator of the motor forms an intermediate bridge in which one of the pivots of certain wheels is pivotally mounted, the other pivot being mounted in one of the base plates. This design therefore makes it possible to economize in regard to one intermediate bridge, but it does not substantially simplify the structure of the movement, nor does it permit any reduction in thickness.